This invention concerns canvas stretching frames, and particularly a bracing system for relatively large canvases, to prevent pulling inward of the peripheral stretcher bars due to tension.
Canvas stretcher frames have previously used bracing for large canvases. However, these were limited by several factors. The braces, typically in a cross or X configuration in the frame, comprising a pair of brace bars orthogonally arranged relative to the peripheral stretcher bars, usually crossed over one another with routed out sections of each brace, in a manner such that the two crossing braces lay in the same plane. Where the ends of the braces met the stretcher bars, typically each brace had a protruding tongue or tenon at its end, which was received in a routed out recess or mortise in the stretcher bar at that location, dedicated to that purpose.
In conventional stretcher bar bracing systems there was no specific provision for addition of further braces beyond the two crossing braces described. In very large canvases further bracing is often needed, requiring custom-made additional braces, further routing out of components to receive bracing, etc.
The present invention provides a relatively simple and easily used bracing system for large canvas frames, wherein the bracing bars are modular in nature and can be added as needed, and wherein braces do not cross over one another.
The peripheral stretcher bars in the system of the invention each have a groove formed on the inner side, so as to face inwardly toward the interior of the space behind the canvas. These grooves are employed to receive bracing bars wherever needed, and in as great a number as needed, and these can include angled braces. Thus, at the back of a canvas frame of the invention, a contiguous groove runs completely around the inner periphery of the frame.
The braces useful for these canvas frames are relatively simple bars, but with tabs or tongues at their ends, insertable into the grooves of the stretcher bars which make up the canvas frame. In the invention, in one typical application, a single brace will extend through the entire length or width of the stretcher bar frame. The remaining bracing is accomplished between that brace, typically centrally located, and the peripheral stretcher bars which are parallel to that single brace, these additional braces being perpendicular to the center brace. In other applications, two or three or four full-length braces can be assembled to retain stretcher bars from pulling inwardly in a long dimension of a large canvas. Then, shorter sections of brace can be inserted in the perpendicular direction, completing the bracing of the entire frame. To receive the additional bracing, the braces themselves have grooves along their side edges, and these grooves receive the tabs or tongues of the additional, smaller braces that are inserted as described above.
In a variation of the above, the bracing can be accomplished with a series of braces all of which are shorter than the full dimension between parallel stretcher bars. A pattern or matrix of the shorter braces can be put together, if desired, all fitting together with the tab and groove connections, so as to build a bracing system that retains all four frame stretcher bars from pulling inward under tension, without any single brace extending from bar to bar.
By this modular set of components, the bracing of a large canvas is made much more efficient, the bracing system can be made stronger, and the modularity of the components allows a framing shop to build a multiplicity of different sizes of fully braced frames from stretcher bars and standard brace components held in inventory, or a customer can purchase components to build a braced frame as needed. This is in contrast with the conventional situation in which a large frame often has to be custom built, with custom-formed bracing.
It is thus among the objects of the invention to improve the construction of braced canvas frames, and to modularize a bracing system so as to allow braced frames to be put together in a modular manner without custom-made components. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings.